1. Field of the Invention
The present invention relates to a reduction gear mechanism.
2. Description of the Related Art
Conventionally, a plurality of gears is supported by respective different rotational axes in a reduction gear mechanism, which reduces the speed of a motor to transmit the driving force to components to be driven. This inevitably leads to the extensive arrangement of the series of reduction gears that extend considerably in the direction perpendicular to the rotational axes of the gears. However, it is often difficult to find a sufficiently large space to accommodate the series of reduction gears in instruments in which the reduction gears are to be arranged. For example, in the case of reduction gears provided in a telescopic portion of a zoom lens barrel between a motor and a component to be driven by the motor, the gears are sequentially arranged in a circumferential direction about an optical axis of the zoom lens. When it is desired to reduce the length of the circumference or the diameter of the lens barrel, the space in which the series of reduction gears are arranged must be kept as small as possible.
Accordingly, it is an object of the present invention to provide a reduction gear mechanism which achieves a high degree of freedom for arranging a series of reduction gears and, in particular, helps keep the space required to arrange reduction gears as small as possible with respect to the direction perpendicular to the central axes of the gears.
In order to achieve the above-mentioned object, a reduction gear mechanism is provided, including at least first and second axes which extend parallel to each other; one of the first and second axes rotatably supports at least two gears arranged one after the other in the axial direction thereof, the at least two gears being independently rotatable with respect to each other, and the other of the first and second axes rotatably supports at least one gear; and the gears provided on the first and second axes being engaged with each other in such a manner that the gear supported on one of the first and second axes successively and alternatively engages with the gear supported on the other of the first and second axes.
In an embodiment, each of the first and second axes rotatably supports two gears arranged one after the other in the axial direction thereof.
In an embodiment, each of the gears supported by the parallel central axes is a double gear having a larger gear portion and a smaller gear portion, the smaller gear portion of the double gear supported by one of the central axes engaging with the larger gear portion of the double gear supported by the other central axis.
In an embodiment, in each of said double gears, the larger gear engages with a preceding gear and the smaller gear engages with a succeeding gear, with respect to the direction of driving transmission.
In an embodiment, the gears supported by the central axes are identical to each other.
The reduction gear mechanism can be arranged in a lens barrel.
In an embodiment, the lens barrel includes a bi-directional motor; a first sub-lens frame and a second sub-lens frame for supporting a first sub-lens group and a second sub-lens group, respectively, the first and second sub-lens groups functioning optically in a mutually close position and in a mutually distant position, in the optical axis direction; and a sub-lens group driving mechanism which moves the first and second sub-lens frames to the mutually close and distant positions, and moves the first and second sub-lens frames integrally in the optical axis direction in the mutually close and distant positions, as the bi-directional motor is actuated. The reduction gear mechanism is provided between the bi-directional motor and the sub-lens group driving mechanism in the zoom lens barrel.
According to another aspect of the present invention, a reduction gear mechanism is provided, including at least two gear supporting axes which extend parallel to each other; and at least three gears, a first gear and a third gear thereof being rotatably supported on the first gear supporting axis at different positions in an axial direction, the first and third gears being independently rotatable with respect to each other, and a second gear thereof being rotatably supported on the second gear supporting axis, wherein the first gear engages with the second gear, and the second gear engages with the first gear and the third gear.
In an embodiment, the reduction gear mechanism further includes a forth gear which is rotatably supported on the second gear supporting axis at a different position in the axial direction with respect to the second gear, the fourth gear being independently rotatable with respect to the second gear, and wherein the third gear engages with the second gear and the fourth gear.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 2000-289384 (filed on Sep. 22, 2000) which is expressly incorporated herein in its entirety.